Stands utilized in medicine and especially for neurosurgery are usually balanced before they are actually used. Such balancing is as a rule required in order to compensate for the forces which are caused by the loads, such as a surgical microscope, arranged on the stand. These forces are compensated so that an approximately force-free guidance of the stand and the load mounted thereon is possible for the particular operator. After being balanced, the entire stand including the load arranged thereon can stay in place in each possible practical position. Balancing is achieved by a manual or electric motorized displacement of counterweights or by pretensioning springs in order to produce a neutral state of equilibrium corresponding to the particular load on the stand.
A stand wherein such balancing before actual use is achieved manually, is, for example, disclosed in U.S. Pat. No. 4,339,100.
Manual balancing by the user is performed by moving the individual axes of the stand one after the other by hand in a prescribed sequence into specific positions. For this purpose, the user releases the corresponding electromagnetic brakes of the axis in order to release that particular axis. The user draws a conclusion as to the actual balanced or unbalanced state by observing the behavior of the axis. In this connection, a return movement of the axis can show that a stable equilibrium is present. A further tilting of the axis indicates that an unsteady equilibrium is present. However, an equilibrium state is desired wherein the gravity center of the axes or of the system of axes plus the applied loads producing torque lies at the pivot point of the axis or on a defined straight line through the pivot point of the axis. The first case is identified in the following as a neutral equilibrium state. The load application points and/or points where balancing forces are applied must be moved with respect to the axis to be balanced in dependence upon which state is present and which axis should be balanced. This is repeated until the axis no longer moves after a displacement. If this is the case, then the total gravity center of all masses, which apply a torque to an axis, lies in the particular axis or, alternately, on a defined straight line through the pivot point of the axes.
The manual balancing procedure is relatively complex to carry out, time consuming and is burdened with certain inaccuracies.